During adrenergic stimulation, blood flow in the small intestine is initially reduced but as stimulation continues flow tends to return to normal. The proposed research is directed towards determining a) whether this type of response is unique to the small intestine or whether it occurs also in stomach, large intestine or spleen b) the mechanisms responsible, e.g. opening of shunt vessels, relaxation of initially constricted vessels, or relaxation of series coupled vessels. The approach involves electromagnetic flow meters to determine total flow, isotopic methods to determine flow distribution and microscopic, histologic and angiographic studies to determine which vessels are involved. These methods will also be used to determine the relative distributions of alpha and beta adrenergic receptor activity in the intestinal wall. The effects of agents which affect cyclic AMP accumulation would also be studied to determine whether cyclic AMP is related to splanchnic beta adrenergic responses. The overall effects of adrenergic stimulation on the distribution of splanchnic flow and its relation to cardiac output will be determined with electromagnetic flowmeters and with isotopic methods. These objectives are related to the long-term goal of determining the role of adrenergic stimuli in the control of the regional circulation and of the circulation as a whole.